Journal of Applied Physiology, Vol 51, Issue 3 577-583, Copyright © 1981 by American Physiological Society
Endotoxin reverses the decreased tolerance of rats to greater than 95% O2 after preexposure to lower O2
L. Frank
Bacterial endotoxin has a marked protective effect against pulmonary O2
toxicity in rats placed directly in atmospheres of greater than 95% O2. To
determine whether endotoxin treatment during exposure to relatively low
levels of hyperoxia would protect rats from the accelerated O2 toxicity
that normally occurs when these rats are transferred to greater than 95%
O2, we gave endotoxin or saline 1) during exposure to 40% O2 (5 days), or
2) during exposure to 40%-60%-85% O2 (2 days at each level). Saline-treated
rats showed significantly decreased tolerance on transfer to greater than
95% O2 [LT50 = 47.5 h (exposure 1) and 48.5 h (exposure 2)] compared with
normal nonpreexposed rats (LT50 = 66 h). In contrast, endotoxin-treated
rats showed a marked tolerance on transfer to greater than 95% O2 [% of
rats surviving 72 h = 14/16 (88%) endotoxin-treated vs. 2/16 (13%)
saline-treated]. The endotoxin-treated rats, unlike the saline-treated
rats, showed significant elevations in lung superoxide dismutase, catalase,
glutathione peroxidase, and glucose-6-phosphate dehydrogenase levels after
the O2 preexposure periods; this may account for their significantly
improved tolerance when challenged with greater than 95% O2 exposure.
